This invention relates to a process and an apparatus for the recovery of a lower melting point metal or alloy from material in which it is present with a higher melting point metal or alloy, e.g. as in the scrap or waste recovery of tin from tin-plated steel or copper from copper-coated steel wire.
Chemical processes for the recovery of tin from tin plate are known, the most commonly used one involving the removal of the tin from tin plate in a solution of sodium hydroxide and reclamation of the tin by electrolysis. This process has been used to recover tin from press trimmings, but increasingly now chemical-resistant lacquers are being used to coat tin plate and this reduces the effectiveness of the process.
Moreover, known chemical processes cannot be used easily on a commercial basis for reclaiming the tin from used tin cans extracted from refuse because:
(a) tin cans have soldered and rolled interlocking seams which restrict the penetration of the de-tinning solution thereby inhibiting tin removal, PA1 (b) cans extracted from refuse contain up to 30% by weight of organic and inorganic debris: this debris contaminates and degrades the chemicals used in the de-tinning process, PA1 (c) as with press trimmings, the lacquer on the cans is difficult to remove chemically.